By Michelle Koidin Jaffee
In certain patients with significant tremor, University of Florida neuroscientists have identified a new technique to quantify dysmetria — an inability to make a movement of appropriate distance, such as touching a finger to a target object — and whether dysmetria is the result of tremor or from a dysfunction of the cerebellum in a nervous system disorder called essential tremor.
In a new Annals of Neurology study, lead researcher Evangelos Christou, Ph.D. and colleagues at the Norman Fixel Institute for Neurological Diseases at UF Health describe using deep brain stimulation to determine the source of the dysmetria in patients with essential tremor, a disorder that causes involuntary shaking.
The study lends insight into essential tremor, the most common trembling disorder, and other disorders of the cerebellum, the region of the brain that controls coordination and balance. The team ran experiments comparing 19 participants diagnosed with essential tremor and undergoing thalamic deep brain stimulation with 19 healthy control subjects, examining rates of dysmetria and tremor.
For a patient with significant tremor, if they slowly reach to touch a finger to a target, their hand will start shaking, and if they hover over the target too long, their finger will shake, Christou said. This could look like dysmetria, but in reality be tremor.
“What we did here was to shorten the duration to the target by asking the participants to do fast movements to the target and then reverse it so they wouldn’t hover over the target,” he said. “This doesn’t allow tremor to kick in and influence the quantification of dysmetria, the gold standard neurological sign of cerebellar dysfunction. Thus, we can quantify dysmetria from tremor, which allows us to make inferences about dysfunction of certain brain locations.”
“The results have important implications for the understanding of essential tremor and other cerebellar and tremor disorders,” said Christou, a professor in UF’s department of applied physiology & kinesiology.